Spark Plug IndexingMy question is about spark plug reach. I recently removed my intake, and while looking at one valve that was near max lift, I could see the electrode was at least 1/8 inch in the threaded hole. I removed it and measured how deep my spark plug hole was-it was almost an inch. I'm using a very early pair of CNC-ported and bowl-blended Patriot aluminum heads. How far should the electrode protrude into the combustion chamber?

Also, do you index your spark plugs? Do the OEMs index plugs? If there were free power in indexing your spark plugs, you'd think the OEMs would all do it.

My motor is a 355 small-block Chevy running 10.5:1 compression, a Comp Cams 286H-10 single-pattern cam, 1.6:1 roller rockers, an Edelbrock Air-Gap intake (fully ported and gasket-matched), and a Proform 750-cfm carb. The exhaust is Sanderson full-length headers dumping into a 2.5-inch MagnaFlow cross-pipe and mufflers. Spark is provided by an MSD Pro Billet distributor with a 6AL box. The front of the motor is buttoned up with a Meziere electric water pump and electric fans.
Jeff Williams
Northern California

There are two considerations: first, the depth of the plug in the hole; second, the orientation of the side electrode in the combustion chamber. Ideally, the top of the spark plug's male threads should be flush with the top of the hole's female threads (even with the chamber roof, neither protruding beyond the hole nor recessed below the top of the hole). But due to normal machining variations on the male and female threads and the fact that the axis of the spark plug hole is rarely perpendicular to the chamber surface, this can vary slightly-generally some small portion of the threads ends up exposed. Also due to manufacturing tolerances and where the lead-in thread begins, an individual plug's side electrode final orientation within the combustion chamber after tightening will vary from plug to plug and chamber to chamber.

2/8Spark plug indexing may be needed to avoid side-electrode contact with high-dome pistons. Some theorists claim positioning the electrode in relation to the intake or exhaust valve may also be worth some power-at least on old-school chambers. To keep track of the electrode position, mark the plug's rear shell in line with the side electrode's open end.

A significant mismatch between the spark plug and hole thread can cause detonation-promoting hot spots. If the plug protrudes too far into the chamber, piston interference is also a possibility. If the plug is recessed into the hole, this could shroud the spark, calling for more ignition lead than normal.

Today, nearly all domestic aftermarket aluminum heads are machined for 3/4-inch-reach, 5/8-inch hex, 14mm, gasketed spark plugs (Champion Y series or equivalent). A good heat-range starting point for a normally aspirated, high-performance small-block Chevy running on pump gas would be a Champion RC12YC, an Autolite 3924, or a competitive equivalent. These are projected-nose plugs. Blown, power-adder, full-race, or any applications using high-dome pistons should consider colder and/or nonprojected tip configurations.

Whether the side electrode requires special orientation or indexing within the chamber is controversial. Everyone agrees that it is sometimes necessary to control electrode orientation on extremely high-compression engines using pop-up pistons-not to gain power but to keep the dome from contacting the side electrode and closing up the plug gap. The advent of angle-plug heads and (for racing) extremely small-volume combustion chambers has minimized the need for this.

In the past, some maintained there was power to be had from (depending on the theorist) pointing the open end of the side electrode toward the chamber's squish area or toward the exhaust side. Again, with modern quick-burn chambers, the current thinking is there's usually no discernible power difference, but the final arbiter is, of course, actual dyno testing of the individual combination.

If desired, specific plug electrode orientation can be controlled by using varying-thickness spacer washers, available from Moroso and other aftermarket sources. Moroso PN 71910 is a flat washer assortment for gasket-seat, 14mm spark plugs. For 14mm, tapered-seat spark plugs, use Moroso conical washer assortment PN 71900. Remember that adding washers moves the plug backward deeper in the hole, which as noted above could call for more ignition lead. Finally, look into using E3 spark plugs, which use a patented Edge-to-Edge electrode design that eliminates the need for indexing.

Pinion AngleAt times, I read in HOT ROD about the pinion angle needing to be 2 to 3 degrees. I am going to build a set of upper control arms for a '75 Chevy Caprice because I raised and leveled the rearend of the car 2 inches and it always did have a misaligned pinion-to-driveshaft angle. Now the pinion is sitting at a really negative down angle. The shocks are within an inch or so of being fully extended. Is there some reason I shouldn't make the pinion line up exactly with the driveshaft?
John J. Pellegrino
Blairsville, PA

6/8Correct driveshaft angularity is important for strength and reliability. For most daily street use, the plane of the trans output shaft (A) and the rearend pinion shaft (B) need to be parallel within ±1 degree (2 degrees total deviation). The angle of offset between the driveshaft and U-joints (C) needs to be between 1 and 5 degrees.

You don't want everything totally lined up. U-joints need a slight amount of angularity to work right. If the trans output shaft, the driveshaft, and the rearend pinion flange are all exactly in line, the needle bearings will brinell into the cross because they can't roll freely. Instead, the trans output shaft and the pinion should be slightly offset, yet still parallel to each other in the same plane. The amount of allowable total offset between the driveshaft and U-joints varies: Low-speed shafts such as a steering column intermediate coupler can work with fairly high angles, but for long-term reliability on a high-speed driveshaft installed in a street car, the experts at Wenco suggest a total offset angle of no less than 1 degree and no more than 5 degrees. For example, if the total offset of the driveshaft is 5 degrees, to maintain everything in parallel, the U-joint angles at the trans end and the pinion end both need to ideally be 2.5 degrees. In the real world, the angles at each end can usually deviate ±1 degree without serious vibration.

Note that the angles discussed above are in reference only to the trans, the rearend, and the driveshaft that connects them, not any angle relative to the ground. However, the rearend pinion and driveshaft angles in relation to the ground can be important for proper chassis reaction in a dedicated racing application. A drag race-optimized rear suspension usually wants a nose-down pinion angle at rest because the pinion nose tends to rotate upward under hard acceleration. Nose down means that the pinion angle relative to the ground is less than the driveshaft angle relative to the ground. It does not necessarily mean that the pinion nose actually points downward in relation to the ground; in some instances the pinion nose relative to the ground will statically point up, but it's still considered nose down if the driveshaft angle relative to ground remains higher than the pinion angle relative to ground.

7/8Check driveline phasing using a magnetic angle finder (Sears Craftsman PN 39830 or equivalent). Hold the device flush against the trans output shaft and the rearend pinion shaft. The sum of the angles should be 180 degrees for the driveshaft to be perfectly parallel in the same plane. A common protractor can be used to scope out the offset angle.

440 Chrysler Into Early CoronetWhere can I locate motor mounts to install a 440 Chrysler engine into a '65 Dodge Coronet? The car now has the 318 wide block in it. I would really like to get bolt-in mounts that will fit the pads that are in the frame.
Don Friday
Luther, MI

A Chrysler B/RB big-block fits the '63 to '65 B-Body (includes Coronet) by using the same insulators and K-member as the 318. Only the engine brackets differ. Schumacher offers the bolt-in, factory-style replacement brackets for this swap, as well as other swap-related parts like headers and conversion transmission mounts. Remember that the big-block rear auto trans or bellhousing mounting pattern is different from the 318 polysphere or LA small-block motor.

Disc Brakes For Chevy PickupsI am building a '71 Chevy C10 for the street and strip. The hubs have a 6-on-5.5-inch bolt pattern with drum brakes. I can't find many wheels that I like with that bolt pattern. Can I get the spindles and brake system off a newer truck to get a five-lug bolt pattern and disc brakes? If so, can I use the ball joints and tie-rod ends for the '71? If not, please tell me what my options are.
Scott Keenan
Matteson, IL

Front disc brakes were standard factory-installed equipment on all '71-and-later Chevy pickups. During your truck's lifetime, someone either put an earlier frame under a '71 cab, put the later cab on an earlier frame, or installed the front crossmember and drums from a '67 to '70 onto the later frame. Regardless, you have a mismatched combination. For the purposes of this discussion, I will assume the front end actually installed on your truck is in fact the '67 to '70 version.

The most popular five-lug retrofit is the '73 to '87 C10 1/2-ton, two-wheel-drive, truck front disc brake setup. It is widely available, and the heavy-duty versions are better designs than the two-year-only '71 to '72 setups. Starting in the late '70s, some (but not all) of these trucks came with lighter-duty brakes than previously. You want the heavy-duty steering knuckles and rotors with a 5-on-5 lug pattern (ID by rotor thickness: 11/4-inch-thick rotors for the heavy-duty option; 1-inch-thick rotors on light-duty models).

There are several ways to go on this conversion, from simple to complex:
At the basic level, grab the late steering knuckles (spindles) and everything that attaches to the spindles from the later donor truck. The knuckles will bolt to your existing early upper and lower control arms by using the corresponding late-model ball joints from the donor truck.

Alternatively, grab the late-model upper and lower control arms with the knuckles and brakes attached. The entire assembly will bolt on to your early frame.

For a high-end conversion, Golden State Parts says it is possible to adapt a '73 to '87 crossmember (plus everything that attaches to the new crossmember, including the steering linkage, suspension, and brakes) to the '67 to '70 frame. Some attachment holes for the late crossmember are in a different location, but you can drill any necessary new holes in the old frame after first carefully centering the replacement unit in the same location as the original crossmember.

If retaining the original crossmember (options 1 or 2 above), some alterations to the steering linkage are required. The original '67 to '70 outer tie-rod ends have 5/8-inch threads; the late-model truck tie rods have 11/16-inch threads plus a different taper on the ball seat that attaches the tie rod to the steering knuckle. Classic Performance Products (CPP) sells custom hybrid billet steel tie rod adjuster sleeves with 11/16-inch lefthand threads at one end and 5/8-inch righthand threads at the other end. Several different lengths are available. With this setup, use your original outer 5/8-inch tie rods as the inner tie rods.

You will also need a disc brake-compatible master cylinder, a power booster, and a proportioning valve from either a '71 to '72 truck or the donor vehicle. It is best to change this out as an assembly, as there were several different pushrod lengths available as well as different suppliers (Bendix or Delco Moraine). At worst, an aftermarket adjustable pushrod may be needed.

If you don't want to piece together all these parts from multiple sources, CPP offers integrated kits with a variety of brake and suspension options, including dropped spindles. More detailed information on Chevy front disc brake retrofit options can be found by searching the discussion threads at www.67-72chevytrucks.com.

And don't forget to have the rearend's axle-shafts redrilled to the 5-on-5 pattern to match your new front end.

5.3L LS Truck MotorI have an '02 LS truck motor, which I think is the same in all aspects to the 5.7L LS1 and LS6 except for the slightly smaller bore size and top end. I am looking to obtain 11:1 to 12:1 compression and keep it naturally aspirated and fuel-injected. I want it to stay dirt cheap and swap as many used parts as I can.

8/8GM 5.3L Vortec truck engines are a great starting point for a budget LS-series buildup.

Are there any parts from an LS1 or LS6 that will benefit me? Everybody swaps out the heads to a set of LS1s or aftermarket heads, but can these truck heads be machined to give the same benefit? The sodium-filled valves in the LS6 are nice, but they are really a luxury.

To reach my compression goal, are pop-up pistons my only option or is there a stroker kit available? Would going one way or the other affect reliability? If the 6.0L LS truck crank is longer, can it be used as a stroker crank? How much power and rpm can the stock 5.3L short-block handle?

This engine will be going in a stripped roadster for Saturday night stoplight bashing. I have a four-speed ready. I am building an aluminum intake with the eight individual stack design similar to what Kinsler and Enderle have designed but with a few differences. It looks supercool-and for only $600 in materials compared with, um, $3,500 for what?

I was also planning on using a Comp Cams Mutha Thumpr cam for that really mean sound and probably get the top end package of rocker arms and pushrods from Comp as well. I plan to install long-tube headers. I would like the motor to rev way high if it can stand it reliably. I was thinking to achieve output in the 450hp range, but hopefully much higher.
Jonathan Bednarz
West Texas

All production LS-style engines except for the 4.8L and 7.0L have the same 3.622-inch stroke (see table), so there's no benefit to installing a 6.0L crank into your engine. The 4.0-inch stroke forged crank used in 7.0L LS7 Corvette engines has about a 1-inch-longer front snout that's designed to work with the LS7's larger, dry-sump oil pump; however, the LS7 crank can be made to work with a normal wet-sump setup by either installing a fabricated 1-inch spacer in front of the LS7 balancer (use an LS7 crank balancer bolt) or by machining the snout to reduce its length by approximately 1 inch (use an LS2 balancer bolt). This conversion also requires a standard LS engine crank gear (PN 12556582), a standard LS oil pump (PN 17801830), and a standard LS2 timing cover (PN 12600325). Aftermarket stroker cranks are widely available that alleviate the need for all this hassle, but whether it's the rare and pricey production LS7 forging or the aftermarket unit, it kind of defeats the purpose of a budget 5.3L buildup. (Kind of like wasting your time stroking an old-school 305 when you can start with a 350.) Note, too, that the really good rectangular-port heads out there capable of feeding large-cubic-inch motors require at least a 4.0-inch bore size. If you want to build a large-displacement LS for a reasonable amount of money, start with a 4.0-inch-bore, 6.0L, cast-iron block.

The most cost-effective enhancement for an existing 5.3L, cast-iron block is to turn it into a 5.7 by overboring the 5.3's stock 3.780-inch-od cylinders to the 5.7L's 3.898-inch size. The School of Automotive Machinists (SAM) sonic-checked a stock-bore 5.3L block for me. It reports "the 5.3L block has 0.270- to 0.290-inch thickness between the cylinders and 0.360 to 0.390 everywhere else." This means after overboring, you'll still have a minimum 0.211 inch of wall thickness remaining, more than enough for hard-core performance use. Big overbores like these won't work on the 5.3L aluminum blocks that began to appear in 2004. They can't be overbored more than 0.010 inch.

LS1/LS2/LS6 heads bolt on to 5.3L engines, and the larger intake valves will clear the smaller, stock, 5.3L cylinder bores. In fact, GM installed LS2 heads (casting No. 243 or 799) on some '07-and-later 5.3s (RPO L33). Admittedly, factory production cams are wimpy in the lift and duration departments, so I also had SAM install a head with 2.02-inch intake valves on a stock-bore 5.3; it reports that at 0.700-inch lift, there was still 0.070 inch remaining valve-to-wall clearance.

Many 5.7L builders actually prefer the 5.3L heads for their smaller, compression-ratio-enhancing combustion chambers. They add the larger intake valves and do a through-pocket port and gasket match to come up with a great, relatively inexpensive, cathedral-port head combo. There are 9-second 5.7L cars out there running heads like these, according to SAM, which is heavily involved in the LS racing scene.

The weak link in the stock LS valvetrain is the marginal pushrods. The rollerized stock rocker arms are plenty stout and lighter than most aftermarket rocker arms. Unfortunately, the stock valvetrain is a net lash (nonadjustable) design. Quality aftermarket pushrods should be used to replace the stock pushrods, and-since they can be ordered in custom lengths-also correct valvetrain geometry on aftermarket hydraulic roller camshafts without the need for an adjustable valvetrain and pricey aftermarket roller rockers.

Idle quality may be a problem with the individual-runner intake and Mutha Thumpr cam. Traditionally, this meant running the fuel-injection in pure Alpha-N mode (throttle position sensor metering only) with a hand-mapped fuel table. But FAST should soon have a direct-port version of its self-learning EZ-EFI system ready; one option is said to be Alpha-N metering but with self-correcting feedback through a wide-band O2 sensor.

These new-gen motors like to rev, and they will make outstanding power. The stock rods with ARP bolts are easily good to 500-plus horsepower. The stock hypereutectic cast pistons are good to 500 hp normally aspirated on good gas, assuming no detonation. The stock cast crank will withstand 750 hp . . . for a while. Collectively, 7,000 rpm is easily possible on a stock short-block. I have seen even otherwise stock 5.3L engines with a good tune-up and a milder aftermarket cam than your projected Mutha Thumpr make more than 430 hp, so you should have no problems hitting your performance goals.